稳定化处理对底泥利用后土壤重金属形态及蔬菜重金属含量的影响

采用小区试验,研究了石灰+钙镁磷肥、海泡石+磷酸二氢钙以及钙镁磷肥3种不同稳定剂对底泥利用带来的重金属污染农田土壤的稳定化效果,以及对空心菜、苦瓜、柿子椒和长豆角4种蔬菜吸收重金属的影响。结果表明,3种稳定剂均能有效降低重金属在土壤中的迁移性和生物有效性,减少蔬菜对重金属的吸收。处理后土壤中的Cd、Pb、Cu、Ni、Zn的弱酸提取态含量均显著降低,最大减少率分别为40.95%、83.87%、67.22%、65.32%和71.61%,Cd稳定化效果最好的处理是LP(石灰+钙镁磷肥),而综合所有元素稳定化效果最优的处理是MP(钙镁磷肥)。处理组蔬菜可食部分中重金属含量均低于《食品中污染物限量》的相关限值,重金属含量的最大减少率分别为85.69%(Cd)、100.00%(Pb)、77.91%(Cu)、64.97%(Ni)、70.93%(Zn),空心菜重金属含量减少最大的处理是LP(石灰+钙镁磷肥),3种处理之间对减少苦瓜、柿子椒和长豆角重金属吸收的差异不显著。空心菜对重金属的平均富集系数大于苦瓜、柿子椒和长豆角。总体来讲,稳定剂可以有效修复底泥利用带来的土壤重金属轻度污染,确保种植蔬菜的食品安全性。重金属轻微污染或稳定化处理后的农田可以根据重金属种类、含量和有效性,种植不同富集能力的蔬菜,以保证其食品安全性。

Effects of stabilization on soil heavy metal fractions and vegetable heavy metal content under amendment with dredged river sediments

A field experiment was carried out to investigate the effects of stabilization on heavy metal fractions in soil and heavy metal con tent in four different vegetables under agricultural applications of dredged river sediments. Results showed that all stabilization treatments reduced heavy metal content in vegetables by diminishing mobility and bioavailability of heavy metals in soils. Compared with the control, Cd, Pb, Cu, Ni, and Zn in acid extractable fraction were apparently reduced in the treated soil, with the maximal reduction rates of 40.95% for Cd, 83.87% for Pb, 67.22% for Cu, 65.32% for Ni, and 71.61% for Zn. The most effective treatment for soil Cd was LP (lime+calcium magnesium phosphate fertilizer), while the best for all other heavy metals was MP (calcium magnesium phosphate fertilizer). The maximal reduction of heavy metals in the edible parts of vegetables was 85.69% for Cd, 100.00% for Pb, 77.91% for Cu, 64.97% for Ni, and 70.93% for Zn. The content of all heavy metals in the plants met the national food safety standards (GB 2762-2012). LP showed the most effectiveness to reduce Cd uptake by water spinach, whereas three treatments did not show difference in reducing heavy metal uptake by balsam pear, bell pepper and carob. Bioaccumulation factors of water spinach for heavy metals were greater than those of bell pepper, bitter melon, and carob. In conclusion, soil stabilization amendments could effectively control the heavy metal pollution caused by sediment applications, ensuring the vegetable safety. In order to secure safe vegetable production, vegetables with different accumulation capacities should be selected for planting in slightly polluted or stabilized farmland soil based on the species, concentrations and bioavailability of soil heavy metals.